From 418f1b1494fc98380dfea559d48386f1ee9e6dcf Mon Sep 17 00:00:00 2001
From: Patrick Strawderman <pstrawderman@netflix.com>
Date: Mon, 6 Mar 2023 13:57:20 -0800
Subject: [PATCH] Call size method on Application to avoid copying instance
 info

DiscoveryClient called getInstancesAsIsFromEureka in a couple locations to get
the number of instances for an application, when Application already has a method
for this purpose that doesn't also incur the overhead of defensively copying.

Additionally, fix a concurrency bug in Application.size, as it was
accessing the underlying instances field without synchronization.
---
 .../src/main/java/com/netflix/discovery/DiscoveryClient.java | 4 ++--
 .../main/java/com/netflix/discovery/shared/Application.java  | 5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/eureka-client/src/main/java/com/netflix/discovery/DiscoveryClient.java b/eureka-client/src/main/java/com/netflix/discovery/DiscoveryClient.java
index 4f22e5bce6..9d9e9d06c1 100644
--- a/eureka-client/src/main/java/com/netflix/discovery/DiscoveryClient.java
+++ b/eureka-client/src/main/java/com/netflix/discovery/DiscoveryClient.java
@@ -1115,7 +1115,7 @@ private void logTotalInstances() {
         if (logger.isDebugEnabled()) {
             int totInstances = 0;
             for (Application application : getApplications().getRegisteredApplications()) {
-                totInstances += application.getInstancesAsIsFromEureka().size();
+                totInstances += application.size();
             }
             logger.debug("The total number of all instances in the client now is {}", totInstances);
         }
@@ -1219,7 +1219,7 @@ private void updateDelta(Applications delta) {
                          * We find all instance list from application(The status of instance status is not only the status is UP but also other status)
                          * if instance list is empty, we remove the application.
                          */
-                        if (existingApp.getInstancesAsIsFromEureka().isEmpty()) {
+                        if (existingApp.size() == 0) {
                             applications.removeApplication(existingApp);
                         }
                     }
diff --git a/eureka-client/src/main/java/com/netflix/discovery/shared/Application.java b/eureka-client/src/main/java/com/netflix/discovery/shared/Application.java
index 57a5c21ec4..2598cc57f0 100644
--- a/eureka-client/src/main/java/com/netflix/discovery/shared/Application.java
+++ b/eureka-client/src/main/java/com/netflix/discovery/shared/Application.java
@@ -187,7 +187,9 @@ public void setName(String name) {
      * @return the number of instances in this application
      */
     public int size() {
-        return instances.size();
+        synchronized (instances) {
+            return instances.size();
+        }
     }
 
     /**
@@ -252,6 +254,7 @@ private void _shuffleAndStoreInstances(boolean filterUpInstances, boolean indexB
         this.shuffledInstances.set(instanceInfoList);
     }
 
+
     private void removeInstance(InstanceInfo i, boolean markAsDirty) {
         instancesMap.remove(i.getId());
         synchronized (instances) {